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UAMOiS GEOtOGtCAl
STATE OF ILLINOIS
DEPARTMENT OF REGISTRATION AND EDUCATION
MINERALOGY OF GLACIAL TILLS
AND THEIR WEATHERINGPROFILES IN ILLINOIS
Part I. Glacial Tills
H. B. Willman
H. D. Glass
John C. Frye
ILLINOIS STATE GEOLOGICAL SURVEYJohn C. Frye, Chief URBANA
CIRCULAR 347 1963
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MINERALOGY OF GLACIAL TILLS ANDTHEIR WEATHERING PROFILES IN ILLINOIS
Part I. Glacial Tills
H. B. Willman, H. D. Glass, and John C. Frye
ABSTRACT
The mineralogy of sand, silt, and clay fractions is usedto characterize the tills in Illinois that were derived from sev-
eral source areas. Tills from the northwest are distinguished
by relatively high percentages of montmorillonite, epidote, andcalcite, from the Lake Michigan basin by relatively high percent-
ages of illite and dolomite, from Green Bay by the presence of
abundant vermiculite, and from the Saginaw-Lake Erie lobes byrelatively high percentages of garnet and illite. Within the state
many of the stratigraphic units are also distinguishable by their
mineral composition.
INTRODUCTION
Throughout most of Illinois the deposits lying immediately below the sur-
face consist of loess or glacial drift of Pleistocene age. These near- surface de-
posits are important sources of construction raw materials; they are involved in
virtually all types of construction work; they serve as raw material for ceramic pro-
ducts; they serve as aquifers and aquitards for ground-water supplies; and they
are the parent materials for most of the soils of the state. Because of the impor-
tance of these deposits in Illinois, the State Geological Survey has been engagedin a regional study of their mineralogy, particularly of the sand, silt, and clay
fractions that compose the predominant part of their bulk. Mineralogical data onIllinois loesses were reported in Circular 334 (Frye, Glass, and Willman, 19 62)
and the present report describes the results of studies of the glacial tills. Thesecond part of the present study will describe the mineralogy of the weatheredzones in the tills and of the accretion-gley deposits on them.
In addition to describing the mineralogy of the matrix of the tills in various
parts of the state, the mineral composition is used to identify the areas crossed bythe glaciers-the source areas of the deposits. Furthermore, the contrasts in the
1
ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
ir-s^^->:::>>:?>'::>>^?>^^deposition only
DUD '''t~"U''.*':,r.:r.
Fig. 1 - Time-space diagram of post-Nebraskan Pleistocene deposits in Illinois.
Time control for the Wisconsinan is based on radiocarbon dates; all radic
carbon dates used were determined in the Washington laboratory of the
U. S. Geological Survey. The diagram is arranged north-south, but it is
a composite of an east-west belt the entire width of Illinois. Outwashdeposits, alluvium, and dune sands are not shown.
MINERALOGY OF GLACIAL TILLS 3
mineralogy of the several tills can be used in many places to identify the various
stratigraphic units within the till deposits.
Prior to the present study, few mineral analyses of Illinois tills have beenavailable. In order to evaluate the geographic and stratigraphic variations in
composition of the tills, mineral analyses of more than 350 samples from localities
throughout the state were made. Some of these analyses were published in a report
discussing gumbotil, accretion-gley, and the weathering profile (Frye, Willman,
and Glass, 1960).
The X-ray analyses were made by Glass, the heavy-mineral separations
and counts were made largely by Constantine Manos, the light-mineral counts
were made by James Bloom and Manos, and the chemical analyses were made by
L. D. McVicker. We express our thanks to George E. Ekblaw and Paul R. Shaffer
for helpful suggestions during the progress of the work.
STRATIGRAPHY
The stratigraphy of the glacial deposits in Illinois is complex and diversi-
fied because the state was invaded by glaciers during all four major stages of
Pleistocene glaciation (figs. 1 and 2) and by lobes from different directions. Dur-
ing the Kansan, Illinoian, and Wisconsinan Stages, ice sheets advancing from the
northeast spread over large areas of Illinois. The Illinoian ice, reaching nearly
to the southern tip, covered about 90 percent of the state. During the Nebraskanand Kansan Stages, glaciers advancing from the northwest spread over parts of
western Illinois. With the exception of a small area in western Illinois, whereKansan drift is at the surface, the older drifts were everywhere overridden by the
Illinoian ice sheet. Thus western Illinois, and a bordering area in eastern Iowa,
is the only region south of the Driftless Area of Wisconsin and Illinois in whichtills from northwestern source areas are overlain by till from northeastern areas.
The stratigraphy of the Wisconsinan loesses of Illinois has been described in a
previous report (Frye, Glass, and Willman, 1962).
Nebraskan
The Nebraskan glacier appears to have invaded western Illinois (Horberg,
1950, p. 100; Flint and others, 1959), but its deposits have been so extensivelyeroded that the area it covered is highly indefinite. Only a few exposures havebeen identified as Nebraskan till (Bell and Leighton, 1929; Wanless, 1957) andmany of these are questioned. Deeply weathered gravel beneath Kansan till appearsto represent Nebraskan outwash in a few localities. None of our samples werecollected from Nebraskan till in Illinois, but one sample is from Nebraskan out-
wash near Peoria, and three samples represent Nebraskan till at Dubuque, Iowa.Drift that may be Nebraskan in age has been noted in central Illinois (Hor-
berg, 1953), but the evidence is not conclusive. Inclusions of weathered till in
calcareous Kansan till at Danville have been interpreted as evidence of an easternlobe of Nebraskan ice (Eveland, 19 52), but the age of the till called Kansan hasbeen questioned (Ekblaw and Willman, 1957). The existence in Illinois of an east-em Nebraskan glacier has not been demonstrated.
ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Fig. 2 - Map showing areas of Illinois covered by the several glacial advances.
MINERALOGY OF GLACIAL TILLS
Kansan
The Kansan glacier that advanced southward west of the Driftless Area to
the Missouri Valley in Missouri spread eastward into Illinois, to approximately
the present position of the Illinois Valley (Leverett, 1899; Horberg, 1956; Wanless,
1957; Flint and others, 1959). The mineralogical evidence given in this report
strongly supports this general distribution for the western drift (fig. 2).
A lobe of Kansan ice also entered Illinois from the northeast and spread
westward nearly to Illinois Valley and southwestward to Mississippi Valley. It
appears not to have extended as far south as the later Illinoian glacier, but occui-
rences of the Kansan drift in southern Illinois are so scattered that the position
of the Kansan boundary is indefinite.
The pre-Illinoian glaciation of central and eastern Illinois was recognized
by Leverett (1899) and MacClintock (1929), although they did not specifically
assign the drift to the Kansan. The degree of weathering of the eastern pre-Illinoian
drift has been thought to be no greater than that of the western Kansan, and the
designation of Kansan has become generally accepted.
As overlapping deposits of eastern and western Kansan till have not beendemonstrated, there is at present no evidence as to their relative ages. The Kan-
san record is probably much more complex than has so far been recognized (fig. 1).
Illinoian
The Illinoian witnessed the greatest westward and southward flow of ice
from the region of eastern Canada that occurred during the Pleistocene. The ice
extended westward across Illinois into Iowa and southward until stopped by the
slopes of the Shawnee Hills. The great extent may have resulted from a particu-
larly strong flow of ice from the Erie and Saginaw lobes that diverted the LakeMichigan lobe glacier into a westerly direction.
The distinctive belt of ridged drift that rises above the nearly flat Illinoian
till plain and extends from the Wisconsinan front near Pana southwest to the Mis-sissippi Valley near Belleville appears to be an interlobate complex marking the
zone of contact between the lobes. The pronounced differences in the mineralogyof the till on the two sides of the ridged drift, reported in this study, support the
interpretation of the ridged drift as dominantly morainic and interlobate, which wassuggested by Leverett (1899, p. 73) and long advocated by George E. Ekblaw, rath-
er than dominantly crevasse deposits, as advocated by Ball (1940) and Leighton andBrophy (1961). The mineralogical data do not oppose the concept that the ridges
mark the front of a lobe of ice that remained in southeastern Illinois after ice re-
treat from western Illinois, which was favored by Leverett (1899, p. 74). However,the many distinctive linear features and the absence of definite westward-facingfronts oppose its interpretation as a normal end moraine.
Although the Illinoian drift southeast of the interlobate ridges is essentially
contemporaneous with that to the northwest, it lacks end moraines comparable to
those that were formed during the retreat of the western ice and that serve as a
basis for subdivision of the Illinoian Stage into the Payson, Jacksonville, and Buf-
falo Hart Substages. The moraines represent readvances after intervals of glacial
retreat. Features suggesting stagnation of the ice are widely present in the area
of Payson drift (Leighton and Brophy, 1961). The Buffalo Hart drift, particularly
in the type region in Sangamon and Logan Counties, has a relatively fresh appear-ing morainic topography, not unlike much of the Wisconsinan drift, and suggestsactive ice during its retreat.
6 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
In many localities along Illinois Valley and its tributaries, lUinoian till
overlies calcareous outwash silts and loess deposited during the advancing stage
of the Illinoian glacier. This silt has been correlated with the Loveland Loess of
the upper Missouri Valley (Leighton and Willman, 1950), but the type LovelandLoess is considered to be largely late Illinoian in age (Frye and Leonard, 1952).
A local rock-stratigraphic name is needed for these deposits which in most local-
ities consist of both water-laid and wind-deposited silts. The name Petersburg
Silt is here proposed from an exposure in a road cut just south of Petersburg,
Illinois, that is described in the Petersburg geologic section. At this locality
the Petersburg Silt is overlain by Illinoian till and overlies the Yarmouth Soil.
The name Petersburg has been used informally for these silts in previous reports.
The name Loveland will continue to be used for the Illinoian loess beyondthe limit of Illinoian glaciation where the material is mostly, if not entirely, loess
and represents the deposits of Illinoian age.
In some areas calcareous, fossiliferous silts, thought to occur beneath
Payson till, as in the Carlinville area (Ball, 19 52), have been interpreted as evi-
dence of an interglacial climate, and the underlying till has been classified as
Kansan. Because the underlying till is calcareous and essentially unweathered,
the silts thin and nonpersistent, and the fauna meager, it seems more likely that
these silts represent an interval of ice withdrawal during Payson time and that
the till below as well as above these silts should be classed as Payson.The Jacksonville drift is overlapped extensively by the Buffalo Hart in
western Illinois (Wanless, 19 57) and in this area sand, gravel, and silt deposits
frequently mark the position of the missing Jacksonville till. Fossiliferous silts,
recently named Roby (Johnson, 19 62), separate the Buffalo Hart drift from Jackson-ville drift in central Illinois.
Several soils have been found in the silt sequence of Illinoian age in Neb-raska and Kansas (Frye and Leonard, 1954), but soil zones have not been recog-
nized definitely within the Illinoian sequence in Illinois. If such soils are present,
they may have been misidentified as the pre-Illinoian Yarmouth Soil, because of
the assumption that the first soil beneath the Sangamon must be Yarmouth. As noevidence of leaching of carbonates has been demonstrated in the many exposuresof intra -Illinoian deposits, an alternative possibility is that the Sangamon Soil in
the Mississippi Valley and at its type locality is a composite of the several soils
in the Missouri Valley, which therefore are by definition Sangamonian rather than
Illinoian
.
A soil which may be intra -Illinoian is exposed in the Pleasant GroveSchool Section, the type section of the Roxana Silt (Frye and Willman, 1960, p. 10).
In that exposure the Wisconsinan loess rests on the Sangamon Soil which is de-
veloped on silt leached to a depth of about 10 feet. The lower part of the silt is
calcareous and rests on weathered till which is leached to a depth of about 3 feet.
If the till is Illinoian, and the surface till in this area is Illinoian, the soil on the
till is intra -Illinoian. As the Illinoian till in this area is oldest Illinoian, the till
may have been weathered before deposition of the overlying silt during late Illinoian
time, and the weathered zone therefore would not necessarily be found where the
Illinoian sequence is more complete.On the other hand, the area was covered also by the Kansan galcier, and
the till may be Kansan. In this case, the weathered zone on the till, which is
much weaker than the normal Yarmouth Soil, was partly truncated before deposition
of the overlying silt. It is completely truncated by the silt in part of the exposure.The silt would then probably correlate with the widespread Petersburg Silt. De-
MINERALOGY OF GLACIAL TILLS 7
velopment of the Sangamon Soil on the silt requires that the Illinoian till be
eroded completely before or during early Sangamonian time, which is not improb-
able because of the bluff situation.
The mineralogical data are not conclusive in this case, but the slightly
greater content of garnet than epidote (samples P-1, P-IA) is more characteristic
of Payson till than either eastern Kansan or southeastern Illinoian tills in whichgarnet is generally several times more abundant than epidote. As the locality is
a short distance west of the interlobate ridged drift of the Illinoian, the till can be
Payson, but if Kansan it must be eastern Kansan. The high dolomite content of
the samples may be even more suggestive because dolomite exceeds calcite in
nearly all Illinoian samples, but calcite exceeds dolomite in all 11 samples of
eastern Kansan. The high montmorillonite content is consistent with Payson com-position, but Kansan drift in the bluff areas could be enriched in montmorillonite
by the glacier riding over a possible western-derived loess and thereby modified to
resemble Payson.
Indentification of tills by counting soils assigns automatically the till at
Pleasant Grove to the Kansan. This interpretation may be preferable until the pres-
ence of intra -Illinoian soils in Mississippi Valley is definitely established. Nev-ertheless, intra -Illinoian soils, if present, are likely to be found among those
previously called Yarmouth on this basis.
Wisconsinan
During the Wisconsinan Stage of glaciation, ice from the Lake Michiganlobe spread widely over northeastern Illinois. Two major episodes of glaciation
are indicated in the Illinois sequence:
(1) The earlier, or Altonian, is represented by a sequenceof loesses (Roxana Silt) best developed in the Illinois River
bluffs beyond the Wisconsinan till plain and in the Missis-sippi Valley bluffs below the mouth of Illinois River, by sur-
face drift in extreme northern Illinois, and by isolated oc-currences of drift elsewhere.
(2) The later, or Woodfordian drift, represents the maximumextent of Wisconsinan glaciation in Illinois, except in ex-treme northern Illinois, and includes all the end morainesdeposited in Illinois during the withdrawal of the ice
into the Lake Michigan basin.
Altonian tills.
-
The Altonian drift exposed in northern Illinois was longassigned to the Illinoian, but when the degree of weathering was found to bemuch less than represented by the Sangamon profile on Illinoian drift farther south,it was assigned to an early Wisconsinan age and correlated with the FarmdaleLoess (Shaffer, 1956). Reclassification of the Wisconsinan Stage, among otherfactors, was required by evidence that most of the loess assigned to the Farmdalehad a different lithology and was older than type Farmdale. This made it desirableto apply a rock-stratigraphic term to the northern drift, and the name Winnebagowas introduced (Frye and Willman, 1960, 1963). The Winnebago drift was assignedto the Altonian Substage of glaciation, and because of its slight depth of weath-ering beneath Peoria Loess and a radiocarbon date from similar drift in southern
8 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Wisconsin, it was believed to correlate with the youngest of the Altonian loesses.More recent studies in northern Illinois have shown that the Altonian drift is com-plex with intervals of retreat and readvance indicated by relatively weak morainic
ridges and changes in drift composition. Subsurface studies have shown a prom-inent readvance of the ice at Rockford (Hackett, 1960), and three distinctive till
sheets have been differentiated in the Winnebago drift in Boone and McHenry Coun-ties, largely by detailed lithologic studies of samples from closely- spaced borings
along the Northwest toll road (Kempton, 19 62). Several of the intervals of Altonian
glaciation indicated by the loess sequence may be present in northern Illinois.
However, as evidence of weathering between the Winnebago till sheets is com-pletely lacking, the oldest Altonian loess (Roxana Zone I), which is strongly al-
tered by weathering, probably was deposited before the earliest Altonian glaciation
recognized to date in Illinois.
At Danville, a pre-Shelbyville till, tentatively referred to as the "Danville"
till, occurs in a valley that was incised through the Sangamon Soil profile devel-
oped on Illinoian till and is assigned to the Altonian Substage. This till was first
classed as Illinoian (Eveland, 1952), but later, like the drift in northern Illinois,
was assigned to the Farmdale (Ekblaw and Willman, 1957). As radiocarbon dating
of wood from the "Danville" till indicates an age greater than 40,000 years
(W-197), the "Danville" till may be mid-Altonian in age.
Despite a conflict in radiocarbon dates available from silt exposed at the
Lake Bloomington spillway (Leonard and Frye, 19 60, p. 29), the underlying tills
are pre-Woodfordian in age and appear to lie above the position of the SangamonSoil and Illinoian till encountered in borings. These tills are assigned to the Al-
tonian and may be comparable in age to the "Danville" till.
Because of these occurrences, Altonian glaciers are believed to have cov-
ered a large area in northeastern Illinois (Frye, Glass, and Willman, 1962, fig. 3).
Woodfordian tills. —The Woodfordian drift is classified into morphostrati-
graphic units based on the end moraines and associated drift sheets. A sequenceof about 30 named units is present in the Illinois part of the sequence. Several
minor moraines have not been named, and the larger moraines, such as the Shelby-
ville, Bloomington, Marseilles, and Valparaiso, consist of several superimposedmoraines with traceable crests that also are not named separately. The Wood-fordian drift is an outstanding example of the pulsating, cyclic nature of the re-
treat of a glacier front while the glacier remains active. The rough morainic topog-
raphy is in marked contrast to the generally flatter topography, containing eskerine,
crevasse, and ice-marginal features, of large parts of the Payson and Winnebagodrifts, which may have resulted from stagnation of the glacial ice.
As required by the short time span of the Woodfordian (less than 10, 000
radiocarbon years), individual cycles of retreat, readvance, and end moraine
building must have been much shorter than has been generally assumed (Horberg,
1955). This is further indicated by the absence of leaching or even significant ox-
idation between the drift sheets, with the exception of local evidence of slight
leaching between the Shelbyville drift and the LeRoy-Cerro Gordo drift (Ekblaw and
Willman, 1957).
The absence of any one break in the sequence of moraines that is more sig-
nificant than many of the others in length of time, in extent of retreat and read-
vance, in realignment of the ice front, in change in composition of the drift, or in
MINERALOGY OF GLACIAL TILLS 9
lateral traceability resulted in adoption of the name Woodfordian for drifts pre-
viously differentiated in Illinois as lowan (of Illinois), Tazewell, and Gary (Frye
and Willman, 1960, 1963). The Tazewell-Cary differentiation was widely accepted
in the mistaken belief that a significant time interval separated Marseilles and
Minooka drifts in northeastern Illinois. The Tazewell-Cary differentiation usedin adjacent states appears to correlate more nearly with the Valparaiso Moraine
than with the Minooka Moraine.
Many of the individual till sheets of the Woodfordian have distinctive
lithologies that permit surface tracing as well as identification in buried sequences.Differences in color and in content of clay, silt, sand, pebbles, and boulders maypersist for 100 miles or more, but they also may change abruptly. Mineralogical
characteristics determined in this study show much greater uniformity than mechan-ical analyses and field characteristics and therefore are less useful in differenti-
ating the individual morphostratigraphic units.
Where lithology does not distinguish the individual Woodfordian till sheets,
differentiation is based largely on the sequences of moraines, overriding relations
at intersections of the moraines, and the presence of water or wind deposits with-
in till sequences. The prevalence of readvance before deposition of successivemoraines is indicated locally by sequences of as many as 6 or 7 till sheets sep-
arated by water-laid deposits.
The relative ages of the Woodfordian moraines referred to in this report are
as follows:
Lake Border (youngest)
Valparaiso-West ChicagoManhattanMinookaMarseilles
Farm Ridge
Cropsey-GilbertsMarengoNormalMetamoraBloomington
UrbanaChampaignLeRoy-Cerro GordoShelbyville-V\^ite Rock
The youngest one or two morainic units of the Woodfordian were deposited
north of Illinois along the lake shore in Wisconsin. The first widely traceable
interruption in the withdrawal of the Wisconsinan glacier from the Shelbyville front
is marked by the Two Creeks Forest Bed, which terminates the Woodfordian Sub-
stage. Although short, this interval of ice withdrawal is much longer than those
during the Woodfordian and its wide distribution justifies its recognition as a
substage, named Twocreekan (Frye and Willman, 1960).
Valderan glaciation.
-
The Valderan glaciation, which followed the Two-creekan withdrawal, did not reach Illinois, but meltwaters discharged through
Lake Chicago and its outlet into the upper Illinois Valley.
ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
MINERALOGY
The glacial tills of Illinois have received intensive study with regard to
their stratigraphy, to their morphology, to the geographic pattern of their end mo-raines, and to their age and correlation, but only minor attention has been given
to their mineral composition. The results of 167 analyses by optical methods of the
minerals in the fine and very fine sand (.062-. 250 mm), 369 analyses by X-ray dif-
fraction of clay minerals, dolomite, and calcite, and 7 chemical analyses of the
gross samples, mostly from the tills of Illinois, are reported here. The geographic
distribution of samples used in this study is shown in figure 3, the samples are
described in table 1, and the results of analyses are presented in tables 2, 4, and
6 and figures 4, 5, and 6. Tables 3 and 5 give average analyses by stratigraphic
unit and geographic region. Figure 7 gives the ranges in clay-mineral composition
for Kansan and Illinoian samples, and figure 8 shows the geographic distribution of
montmorillonite concentration in Illinoian and Wisconsinan tills.
The mineralogical studies have
three major objectives: (1) descriptive __ _characterization of the tills in Illinois,
(2) differentiation of the several strati-
graphic units by their mineral composi-tion, and (3) development of information
concerning the source of the materials
in Illinois tills and the direction and
route of movement of the transporting
glaciers.
Tills have a complex mineral
composition and may contain representa-
tives of all the rock and mineral types
that occur in the bedrock of the region
traversed by the transporting glacier.
However, irregularities in the depth andextent of erosion by the glacier from place
to place, direction of ice movement, andamount of local deposition may causesignificant differences in the mineral
composition of the till deposited by a
single glacial lobe. Within the tills of
Illinois, igneous and metamorphic rocks
and limestone and dolomite are dominantamong the cobbles and boulders; quartz
grains are dominant within the sand frac-
tion; the clay fraction is composed large-
ly of clay minerals; and other minerals
have peaks of abundance in different size
fractions.
As analyses of all size fractions
of all samples were impractical, it wasdecided to concentrate on one fraction of
sand and on the clay fraction. Clay is
present in all samples, and even in well
sorted sands sufficient clay for X-ray . 3 - Distribution of sample localities.
MINERALOGY OF GLACIAL TILLS 11
analysis can be obtained generally by use of proper techniques. In the sand the
combined fine and very fine sand fraction (62-250 microns) was found to be the
coarsest material present in sufficient quantity through the entire range of samples,
which include tills, loesses, weathering profiles, and outwash. By use of this
size fraction the analytical data presented in our several related reports are com-parable.
The degree of mineral differentiation was limited by the large number of
samples involved in the study, and emphasis was placed on those minerals mostindicative of differences in source areas. As the heavy minerals in the sand frac-
tions of the tills are not common in Paleozoic sediments, they must have been de-
rived largely from the more distant Precambrian rocks of the Canadian Shield. Var-
iations in the composition of the sedimentary rocks eroded by the ice should be re-
flected in the X-ray analyses of the clay fraction. Geographic differences in clay
minerals were anticipated because of the high nontmorillonite content of Cretaceoussediments in the western region, which contrasts with the abundance of illite andchlorite in the Paleozoic sediments in Illinois and to the east. The dominance of
dolomite over limestone in Lake Michigan lobe drift, in contrast with the dominanceof limestone over dolomite in western drift (Horberg, 1956; Anderson, 1957; Wanless,19 57), reflects variations in the relatively local rather than distant bedrock. Therelation of limestone to dolomite reported by earlier workers was determined bycounts of pebbles, but as shown by the results reported here the relation of cal-
cite to dolomite may be more readily evaluated by the X-ray analyses of the fine
fractions in the tills.
Conventional methods were used in separating the heavy minerals. Thesand fractions of the tills were acid treated, sieved, and heavy minerals sepa-
rated from the 62-250 micron fraction using bromoform. The heavy minerals werempunted in balsam on slides and the percentages determined by counting 200
grains.
Using oriented-aggregate techniques, the amounts of montmorillonite,
illite, chlorite, and kaolinite were calculated from X-ray diffraction data of the
less than 2-micron fraction. Montmorillonite as used here includes all clay ma-terials that expand to about 17A with ethylene glycol. Mixed-layer clay minerals
and expansible chlorite or vermiculite are included therefore with the montmoril-
lonite. Chlorite includes all 14A material that does not expand with ethylene gly-
col, and it includes any nonexpansible vermiculite. Illite and kaolinite are usedas generally accepted. The values for kaolinite and chlorite are combined in the
tables; the values for montmorillonite and illite are given for each. Determinationof carbonate minerals was made by X-ray diffraction analysis of finely ground bulk
samples and, therefore, reflects the composition of the combined sand, silt, andclay sizes. Data are expressed as X-ray counts per second, which indicates semi-quantitatively the amount of calcite and dolomite.
Heavy Minerals
Certain heavy minerals provide an effective means of differentiating tills
from different source areas, even though they comprise much less than one percentof most tills. The usefulness of heavy minerals has been particularly well shownin Ontario by the studies of Dreimanis, Reavely, Cook, Knox, and Moretti (1957).
The large variety of heavy minerals found in the sand fraction of the tills
of Illinois is derived mainly from the Precambrian rocks of the Canadian Shield.
12 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Heavy minerals in the Paleozoic sandstones are largely limited in variety and lowin abundance. The Cambrian and Ordovician sandstones are mostly medium to
coarse grained, and consequently have a low percentage of the sand fraction an-
alyzed in this study. Northeast of Illinois, the Cambrian and Ordovician sand-
stones are not an important source of the sand in the till as they were overlapped
by Middle Ordovician limestones.
Pennsylvanian and Mississippian sandstones and siltstones could, andprobably did, contribute significant amounts to the sand fraction studied, but they
also have a low percentage and limited suite of heavy minerals, generally domi-nated by zircon and tourmaline with minor amounts of garnet.
Contributions from the Paleozoic bedrock, therefore, did not significantly
modify the heavy minerals, either in abundance or species, even where they madea major change in the composition of other fractions of the till. The heavy mineral
suites in the Illinois tills are similar to those reported in the drift of Ontario
(Dreimanis and others, 1957; Dreimanis,19 60) where most of the till is derived
directly from Precambrain rocks.
A relatively thin cover of Cretaceous and Pliocene sands and gravels on the
erosional surface of the Paleozoic rocks is probably the source of the staurolite,
kyanite, and andalusite in the tills from the western source areas. These minerals
are most abundant in the deposits of the earliest glaciers which may have complete-
ly eroded the surficial veneers from large areas. The mineral composition of Cre-
taceous and Tertiary sands in the upper Mississippi Valley is recorded by Andrews(1958).
Our data show that tills deposited by glaciers that invaded Illinois from the
west and northwest can be differentiated consistently from tills deposited by gla-
ciers from the east and northeast by their heavy minerals. The western-deriveddrift is relatively high in epidote and low in garnet. It is also relatively high in
tourmaline, zircon, kyanite, staurolite, and andalusite, but these minerals are
individually low in amount, generally less than 5 percent of the transparent heavyminerals. The western drift generally has a higher content of black opaque min-
erals. Analyses of heavy minerals in the western tills in Iowa are reported byKay and Graham (1943, p. 182) and Ruhe (1956). Ameman and Wright (1959) give
heavy mineral analyses for tills in the Des Moines lobe in Minnesota.The eastern -derived tills in Illinois appear to include deposits from four
lobes. The Green Bay lobe eroded a trough in Maquoketa Shale along the position
of Green Bay, in the area where the strike of the Maquoketa outcrop is parallel to
the direction of ice movement. It is essentially a branch of the Lake Michiganlobe. In extreme northern Illinois, the relatively high epidote content of the
Winnebago drift and of the northern part of the Woodfordian drift suggests deriva-
tion from the Green Bay lobe which has a high content of epidote (Murray, 1953).
The source of the heavy minerals may be in the area north of Lake Superior wherelarge percentages of epidote are reported by Dreimanis and others (1957, fig. 1).
The Lake Michigan lobe deeply eroded a trough in Devonian and Mississip-
pian shales. The presence of a Lake Michigan lobe in Kansan time has not beendemonstrated and the lobe may have first developed during Illinoian glaciation.
Till deposited by the Lake Michigan lobe is characterized by the abundance of
dolomite from the Niagaran (Silurian) and Galena (Ordovician) dolomites along the
west side of the lobe, and of shale from beneath the lake. The heavy minerals
appear to be characteristic of the Precambrian rocks north of Lake Huron, called
the Superior Province by Dreimanis and others (1957, p. 153), and in particular
MINERALOGY OF GLACIAL TILLS 13
they lack the high percentage of garnet present in the Grenville Province north-
east of Lake Huron and Erie.
Most of the Woodfordian tills of Illinois were deposited by the Lake Mich-igan lobe, but a reentrant, marked by converging moraines near Gibson City in
eastern Illinois, appears to represent a contact between the Lake Michigan lobe
and either the Saginaw or Erie lobe. Heavy minerals of the Woodfordian tills in
Illinois have been described by Wascher and others (1960).
The Saginaw lobe, consisting of ice flowing from the Lake Huron basin,
may be the source of the lUinoian till of southeastern Illinois. It contains muchmore garnet than epidote, which indicates its derivation from the Grenville Pro-
vince, but it contains more dolomite than calcite. This combination suggests that
the ice moved from the Saginaw lobe across northern Indiana where the Silurian
formations could supply the dolomite. Farther east in northeastern Indiana and
northwestern Ohio, in the area crossed by the Erie lobe, the Silurian formations
contain more limestone and the Devonian and Mississippian carbonate rocks are
almost entirely limestone.
The Erie lobe appears to have been the source of the eastern Kansan till in
Illinois because it contains the heavy minerals of the Grenville Province and more
calcite than dolomite.
Nebraskan
Three samples of Nebraskan till from near Dubuque, Iowa, are from local-
ities west of the Driftless Area and are representative of we stern -derived tills.
They are similar to the western Kansan in that they contain about twice as muchepidote as garnet (table 3). They also contain a significantly larger amount of
kyanite, staurolite, and andalusite than all eastern drifts. These samples con-tain about 15 percent more hornblende than the samples of western Kansan till.
The common presence of 2 to 3 percent of staurolite distinguishes both westernNebraskan and Kansan from the eastern tills which commonly contain only a trace
of staurolite. The Nebraskan samples also average higher in percentage of black
opaque minerals than the western Kansan and both contain more than the eastern
tills. Diopside-augite minerals are rare in both western Nebraskan and Kansantills.
Kansan
Western. —Western Kansan till commonly contains 2 to 4 times as muchepidote as garnet (10 samples average 10% garnet, 23% epidote, table 3). Theproportion of epidote was highest (3 to 5 times greater than garnet) in samples just
west of the Mississippi River in Missouri and Iowa and in extreme western Illinois
and lowest (li to 2^ times greater) near Peoria. As there was no available garnetin the bedrock of western Illinois, the change in ratio may indicate a lateral changewithin the lobe and that ice flow was more from the north than the west.
The relatively high epidote content generally distinguishes the westernKansan from the overlying Illinoian till as only 12 of 49 Illinoian samples con-tained more epidote than garent, and in 7 of the 12 the difference was only 1 or
2 percent. The difference apparently results from both more garnet and less epi-
dote in the eastern tills, rather than a large increase in one mineral.
14 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
A good example of the Kansan-Illinoian differentiation in western Illinois
is at Eliza in Mercer County, as shown by the following analyses:
Garnet Epidote
Illinoian {P-541) 24% 17%
Kansan (P-538) 8% 23%
The relatively higher content of epidote in the western Kansan till distin-
guishes it even more clearly from the eastern Kansan in which garnet averages 4
times greater than epidote. However, only 4 samples of eastern Kansan till wereanalyzed.
Tourmaline and zircon are generally more abundant in the western Kansantill than in the tills from eastern source areas.
Hornblende averages less in western Kansan till (49%) than in any other
group of samples (table 3), and black opaque minerals are more abundant than in
most of the eastern tills.
As in the Nebraskan till, a low but persistent percentage of staurolite and
andalusite distinguishes the western Kansan from the eastern Kansan till.
Eastern. —The eastern Kansan till, although represented by only 4 samples,
appears to contain 4 times as much garnet as epidote, almost exactly the reverse
from the western Kansan. This reflects the southerly distribution of the eastern
Kansan and therefore contrasts Saginaw-Erie till (rather than Michigan lobe till)
with the western Kansan. Such a large amount of garnet may not be found in the
more northern part of the eastern Kansan till.
The samples of eastern Kansan till have an average of about 6 percent
diopside-augite, which rarely exceeds 1 percent in other eastern tills and is very
scarce or absent in the western tills.
The average of 5 percent hypersthene in the eastern Kansan till is matchedonly in the Wisconsinan Marseilles and Minooka tills.
Illinoian
All the samples of Illinoian till from Lake Michigan lobe drift west of the
interlobate belt contain about equal quantities of garnet and epidote. The greatest
variation is about half again as much of either mineral. Some of the more extreme
variations may result from the glacier riding over the high-epidote western or high-
garnet eastern Kansan till. The heavy mineral contents of the Payson, Jackson-ville, and Buffalo Hart tills are similar and do not differentiate these tills.
The Lake Michigan lobe Illinoian till can be differentiated from the under-
lying eastern Kansan till by its higher percentage of epidote, as shown by the
following analyses of samples at Taylorville, in Christian County:
_Garnet Epidote
Illinoian (P-970) 24% 13%
Kansan (P-9 64) 2 6% 5%
In the Illinoian till southeast of the interlobate morainic complex, garnet
exceeds epidote by 2^ times. Consequently, it generally cannot be differentiated
from the underlying eastern Kansan till which also contains abundant garnet. How-ever, the Illinoian till appears to average somewhat higher than the Kansan in
MINERALOGY OF GLACIAL TILLS 15
content of epidote, zircon, and tourmaline and lower in hypersthene and diopside-
augite.
Tourmaline averages notably higher in all the Illinoian tills than in the
Wisconsinan tills (3% to 1%), but zircon is about the same in both (2-3%).
Although the quantity of each is small (1% or less) the minerals rutile,
titanite, kyanite, staurolite, and andalusite are present more consistently in the
Illinoian tills than in the Wisconsinan tills.
Hornblende appears to be slightly less abundant in the Illinoian than in
the Wisconsinan tills. Except for the Buffalo Hart till, the average hornblende
percentages are generally in the 50 's in the Illinoian and in the 60 's in the Wis-consinan tills.
Wisconsinan
The Winnebago till differs from the Illinoian in averaging slightly higher in
epidote than garnet, but in this and other respects its heavy minerals are similar
to those in the bordering Woodfordian tills. The high content of epidote in the
Winnebago till and in the more northerly part of the Woodfordian tills appears to be
characteristic of the western part of the Lake Michigan lobe and particularly of
till of the Green Bay lobe (Murray, 1953).
The Woodfordian tills differ from the Illinoian principally in averaging
slightly higher in epidote than garnet, whereas the Illinoian averages slightly
higher in garnet. Use of this criterion is complicated in the border area of the
Woodfordian tills because the Shelbyville till, like the Illinoian, averages slight-
ly higher in garnet than in epidote (table 3) . However, there is a distinct changein the composition of the Shelbyville till about at the latitude of Peoria. Shelby-
ville till at Peoria and northward averages distinctly higher in epidote (17%) than
garnet (13%), while that to the south and east averages more than twice as high
in garnet (16%) as in epidote (7%). Consequently, in both areas there is a fair
differentiation from the nearly equal garnet and epidote in the Illinoian. However,east of the city of Shelbyville the Illinoian till has a high content of garnet, so
that the abundance of garnet is not a basis for differentiation.
In the Woodfordian tills of Bloomington age and younger, which were sam-pled in the area north and east of Peoria, the amount of epidote increases andreaches a maximum of about 2|- times more epidote than garnet in the Minooka andValparaiso tills. The amount of epidote decreases again in the Tinley till, but
only two samples were analyzed.In addition to more epidote, the younger Woodfordian tills (Marseilles to
Valparaiso) have about twice as much enstatite and hypersthene as the older Wood-fordian tills. In general the Woodfordian tills have more enstatite and hypersthenethan the Illinoian tills.
The general differences between the Woodfordian and Illinoian tills are
well shown in several sections. In the Farm Creek Railroad Cut Section in Taze-well County, the Illinoian (P-131) contains equal garnet and epidote, whereasthe overlying Wisconsinan (P-138) contains li times as much epidote as garnet
and also more enstatite and hypersthene.At Depue in Bureau County a sample of Bloomington till (P-384) contains
twice as much epidote as garnet, but garnet was equal to epidote in one Illinoian
sample (P-374) and only Ij times epidote in the other (P-376).
Near Danvers in Woodford County, there is a good distinction because the
Shelbyville till (P-558) has the high garnet content characteristic of the southern
16 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
area, but the Illinoian (P-550) has the equal garnet and epidote content character-istic of the area west of the interlobate ridged drift.
Light Minerals
Analyses of the light minerals in the sand fractions show some general
differences, but are perhaps more outstanding for uniformity (table 3). The aver-
ages show potash feldspars ranging from 10 to 21 percent and soda-lime feldspars
from 7 to 9 percent. Although no regional or stratigraphic trends are shown by the
soda-lime feldspars, the potash feldspars are clearly 5 to 10 percent higher in
the Wisconsinan tills than in the older tills. The lowest percentage of potashfeldspars is in the eastern Kansan till, only 5 and 7 percent in two samples.
The relative abundance of the feldspars in the sand fractions is in large
part related to the composition of the Precambrian rocks. From the composition of
the Nebraskan, Kansan, and Illinoian tills, it would appear that the ratio of potash
to soda-lime feldspars is similar in both the eastern and western parts of the
Canadian Shield. The higher content of potash feldspars in the Wisconsinan tills
may indicate a variation in the amount of material contributed by either closer or
more distant parts of the eastern Precambrian.
Clay Minerals
The clay-mineral content of glacial tills in the Midwest has in recent years
been discussed for deposits in Ohio (Droste, 1956), in Indiana (White, Bailey, andAnderson, 1960; Murray and Leininger, 1956; Gravenor, 1954; Harrison, 1960), in
Wisconsin (Brown and Jackson, 19 58), in Minnesota (Ameman and Wright, 19 59),
and in Illinois (Beavers and others, 1955; Brophy, 1959; Frye, Willman, and Glass,
1960; Frye, Glass, and Willman, 19 62; Wascher and others, 19 60; Kempton, 1962;
Johnson, 1961, 1962). However, most of these studies were concerned with pro-
blems of mineral alteration in the development of weathering profiles rather than
the characterization of the unleached tills.
In Circular 334 on the mineralogy of loess (Frye, Glass, and Willman,
1962), the clay-mineral composition of tills in Illinois and adjacent states wasbriefly summarized. We present here a more comprehensive description of the clay
minerals in the tills of Illinois by stratigraphic unit and source province. The clay-
mineral assemblages in the tills reflect a source in the Paleozoic and Mesozoicrocks, generally within a few hundred miles of the point of till deposition. Tills
deposited by glaciers that advanced from the northwest strikingly reflect the ex-
ceedingly high montmorillonite content of the Upper Cretaceous and younger de-
posits over which these glaciers advanced. In contrast, the tills deposited byglaciers that advanced from the northeast contain a high proportion of illite char-
acteristic of the middle to late Paleozoic rocks that occur across Indiana, Mich-igan, northern Ohio, and southern Ontario, and the tills from the north strongly
reflect the illite and chlorite of the Ordovician, Devonian, and Mississippian
shales. In addition to these adjacent sources of clay minerals, the Pennsylvanian
bedrock of Illinois has exerted an important influence on the clay-mineral compo-sition of tills in all but the northernmost part of the state.
MINERALOGY OF GLACIAL TILLS 17
Nebraskan
No samples of Nebraskan till from Illinois were analyzed. In order to
determine the general composition of Nebraskan till a few samples from Iowa,
South Dakota, and northeastern Kansas (fig. 4) were analyzed. These samples
all showed abundant montmorillonite (63% to 86%), minor amounts of illite and
kaolinite, and virtual absence of chlorite (table 5). The Nebraskan till of the
western region appears to be indistinguishable from the overlying Kansan till
which was derived from the same general region.
Kansan
The Kansan till derived from the west is essentially indistinguishable from
the Nebraskan till in the western province. Samples of Kansan till from west of
Illinois are from the type region of Kansas (Frye and Leonard, 1952), and from
South Dakota, Iowa, and Missouri. These samples were uniformly high (62% to
85%) in montmorillonite and contained minor amounts of illite and kaolinite, but
virtually no chlorite
.
In western Illinois (west of the fourth principal meridian) the range in clay-
mineral composition of the Kansan till (figs. 4, 7) is similar to that farther west,
with montmorillonite averaging 65 percent of the clay minerals. A consistent
characteristic of Kansan till in this province is that the amount of kaolinite is
always greater than illite. Eastward in Illinois the percentages of illite and chlor-
ite progressively increase and that of montmorillonite progressively decreases(fig. 9, table 5). Montmorillonite averages only 43 percent at the easternmostextent of the till. This results from incorporation of illite and chlorite from the
local Pennsylvanian bedrock.
The Kansan glaciers that entered Illinois from the east and northeast (fig. 3)
deposited a till that contains a clay-mineral assemblage distinctively different
from that of western Kansan. The clay minerals of the eastern Kansan till are
characterized by abundant illite, some kaolinite and chlorite, and very little or
no montmorillonite. This composition is typical of the clay minerals in the
Paleozoic shales throughout the region lying east and northeast of Illinois. As the
till is traced southwestward toward its maximum extent in Illinois, some mont-morillonite appears in the clay-mineral assemblage (fig. 4, table 5), and it reaches
a maximum of 24 percent in Macoupin County. In this case the local bedrock of
the region crossed by the glacier contains relatively small amounts of montmoril-lonite, and it is judged that pro-Kansan or older loess from the Ancient MississippiValley was incorporated by the overriding glacier.
Illinoian
Glaciers of Illinoian age entered the state from the northeastern corner byway of the Lake Michigan lobe. Farther south in Illinois, glacial lobes that movedby way of Saginaw Bay or possibly the western part of the Lake Erie basin, depos-ited the southernmost till in Illinois (fig. 3). Several glacial pulses entered Illi-
nois during the Illinoian Stage (fig. 1). As they contain different mineral assem-blages (figs. 5, 7), it appears that their configurations and routes of movement,and perhaps also their areas of maximum erosion, were somewhat different.
Preceding the first advance of Illinoian glaciers, but presumably related
genetically to the advancing glacial front, there was extensive deposition of both
water-laid and eolian silts, the Petersburg Silt. In the type region in Sangamon
ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
MONTMORILLONITE
Eastern Kansan
Western Kansan (west of
fourth principal meridian)
KAOLINITE
and CHLORITE
X Western Kansan ( east of
fourth principal meridian)
A Nebraskan
MINERALOGY OF GLACIAL TILLS
MONTMORILLONITE
/
/
/AAA
/\\/ \/\
/ \\/A\/\/\
/v/\X X^/\/\/V{^\/
A./\/\/\A A
VA/ X \//\/\/\/\^ /\ A
\/7\\/\/\/\/\
/ ^\ %/> A "^ A
\7/\/\/\/\/\/\ •'X^J^'*l\
\l
/\\/\/\/\/\/\
• Buffalo Hart
° Southeast
KAOLINITE
and CHLORITE
A Jacksonville
X Payson
ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
MONTMORILLONITE
)e2»-
^,fM:KAOLINITE
and CHLORITE
Valders o Shelbyville
Woodfordian (post- Shelbyville) Winnebago
White Rock • Altonian
MINERALOGY OF GLACIAL TILLS
MONTMORILLONITE
\.W. KAN.
nebr:
(ILLINOIAN ):
fSJSE }
(BUFFALO H/\RT|
KAOLINITE
and CHLORITE
- Three-component diagram contrasting clay-mineral compositions of the
several Illinoian tills with western Kansan (exclusive of the
eastern diluted margin) and eastern Kansan.
22 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
County, the Petersburg Silt is high in montmorillonite, averaging more than 50 per-
cent of the clay minerals, with about 38 percent illite and small amounts of both
kaolinite and chlorite. In western Illinois the montmorillonite ranges up to 85
percent, but unlike the underlying Kansan till it invariably contains some chlorite.
The high montmorillonite content appears to be related to a western silt source byway of the Ancient Mississippi and Iowa Rivers (Frye, Glass, and Willman, 1962),
but, as the front of the Lake Michigan lobe glacier approached and contributed a
progressively larger portion of the deposit, the percentage of montmorillonite de-
creased and the illite and chlorite increased. This progressive upward change is
well illustrated by the samples from Rock Island County (HK-32 to HK-43).The first advance of the Illinoian glacier from the Lake Michigan lobe gave
rise to the till classed as Payson. In Illinois the montmorillonite percentage in
the Payson till shows the largest range (17% to 64%) of any unit studied, exceed-ing even the western Kansan. The montmorillonite content progressively increases
toward the western and southwestern limits of the Payson advance (fig. 8), andthe increase is attributed to the incorporation of materials from the Petersburg Silt
and western Kansan till which were overridden by the advancing Payson glacier.
Although the range in montmorillonite of the Payson overlaps that of the western
Kansan, at any one locality the percentage in the Payson averages lower than that
in the underlying western Kansan till and Petersburg Silt (fig. 9). In Payson till
the sum of chlorite and kaolinite is always less than illite. In contrast, in ex-
treme western Illinois (west of the fourth principal meridian), the western Kansantill contains more kaolinite than illite and has little or no chlorite. Therefore,
the clay-mineral assemblage characteristic of the Lake Michigan lobe is recog-
nizable at least to the Mississippi River.
The Illinoian till in the southeastern region, southeast of the interlobate
area, generally has less montmorillonite than does the Payson till (fig. 8), but
here also there is a distinctive increase in montmorillonite content as the peri-
phery of Illinoian glaciation is approached. Inside the marginal areas the south-
eastern till is uniform and averages 16 percent montmorillonite, in contrast to a
minimum of 17 percent and an average of 36 percent for the Payson till. Inasmuchas the glacier that deposited this till advanced along a route east of the LakeMichigan lobe, it could not acquire montmorillonite from either western Kansantill or western-derived Petersburg Silts, and therefore it reflects the clay-mineral
composition of the bedrock over which it moved.The clay-mineral composition of Jacksonville till differs from that of the
southeastern till only by its somewhat greater montmorillonite and less chlorite-
kaolinite content, but is distinctly different from that of the Payson till which hasmuch more montmorillonite and less illite. The kaolinite-chlorite content of the
Jacksonville is lower than that of any other Illinoian till (fig. 5, table 5), and
therefore it can be distinguished from them by its clay-mineral composition.
The clay-mineral composition of the Buffalo Hart till is regionally uniform
and is characterized by extremely low percentages of montmorillonite (fig. 5,
table 5). The average montmorillonite content is the lowest of all Illinoian tills
and falls within the ranges of only eastern Kansan and Woodfordian. The kaolinite-
chlorite content, averaging about the same as that of the eastern Kansan, is on the
average higher than that of the Wisconsinan tills. The end moraine shows the
highest montmorillonite content within the Buffalo Hart till (figs. 8, 9), probably
due to incorporation of underlying material in the marginal zone.
MINERALOGY OF GLACIAL TILLS
Fig. 8 - Contour map showing percentage of montmorillonite in the surface tills
of Wisconsinan and Illinoian age.
24 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Wisconsinan
The clay-mineral composition of the Wisconsinan tills reflect both strati-
graphic units (fig. 6) and geographic position. These tills were predominantlyderived from the Lake Michigan -Green Bay lobe, but in east-central Illinois someof the till may have had a source in the Saginaw lobe, or perhaps even farther east.
The oldest Altonian tills examined are represented by an inadequate number of
samples to permit firm generalization (fig. 6), but they are similar to Woodfordiantills and presumably were strongly influenced by local bedrock.
The late Altonian Winnebago till in north-central Illinois (the till described
by Shaffer, 1956) contains a clay-mineral assemblage that differs from both the
Illinoian tills and the Woodfordian tills. Winnebago till contains more montmoril-lonite than does the younger Wisconsinan tills, and virtually all of the expansible
material consists of vermiculite or vermiculite-chlorite derived from chlorite and/orbiotite micas. Therefore, the expansible material classed as montmorillonite in
the Winnebago till is distinctly different from the indigenous western montmorillon-
ite that occurs in Payson till, western Kansan till, and we stern -derived loess, but
is similar to the expansible material in the younger Valders till (fig. 6) that wasdeposited by the Green Bay lobe. This relation, together with the absence of
kaolinite (which can be derived from Pennsylvanian and Mississippian rocks) and
the geographic pattern of distribution, suggests that the Winnebago till sampledin Illinois was deposited by the Green Bay lobe.
The Woodfordian tills (with the exception of the White Rock till which re-
flects a major incorporation of Winnebago material) possess a clay-mineral assem-blage different from that of the Winnebago till (fig. 6). In general these tills re-
semble Buffalo Hart till because of their low montmorillonite and high illite con-tent (table 5), but the Woodfordian contains little if any kaolinite. The similarity
in clay-mineral composition seemingly reflects a similar origin Jn the Lake Mich-igan lobe, and the kaolinite in the Buffalo Hart till may merely reflect the fact
that all samples of this till were from areas underlain by Pennsylvanian bedrock.
The Woodfordian tills have an average of 4 percent montmorillonite, andit appears that this expansible material is derived entirely from altered chlorite.
In the peripheral zone of the Woodfordian, particularly in the Shelbyville
Moraine (fig. 6) and the LeRoy, Bloomington, and other moraines where they ap-
proach the limit of Woodfordian glaciation, there occurs a small but significant
increase in the percentage of expansible materials, probably reflecting the in-
corporation of some loess, accretion-gley, and older till materials in the leading
edge of the advancing glacier. A similar relation is shown in extreme northern
Illinois where materials derived from the Winnebago till are incorporated in the
White Rock, Marengo, and West Chicago Moraines. Inside of this peripheral
zone, the composition of the Woodfordian tills is homogeneous and the amount of
expansible material rarely if ever exceeds 5 percent.
MINERALOGY OF GLACIAL TILLS
Fig. 9 - East-west cross section from Vermillion to Hancock County showing dia-
grammatically the percentage of montmorillonite in tills of various ages.
26 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Carbonate Minerals
Based on pebble counts from tills in Illinois and eastern Iowa, Horberg(1956), Anderson (1957), and Wanless (1957) have demonstrated that till from the
Lake Michigan lobe is characterized by more dolomite than limestone whereas the
western tills contain more limestone than dolomite. In order to extend and refine
this method of differentiation, semi-quantitative X-ray diffraction analyses of
calcite and dolomite were made on the bulk samples from all localities used in
this study. This method provides an analysis of the fine sand, silt, and claymaterial in contrast to the earlier studies that were concerned only with pebbles.
Data from these samples confirm the general conclusions of the earlier
studies. Samples from the middle Missouri Valley (Kansas) show virtually no dol-
omite, but the dolomite percentage increases eastward in the western tills. At
the eastern limit of the western Kansan till in Peoria, Putnam, and Bureau Counties,
Illinois, dolomite exceeds calcite and thus reflects additions from the Ordovician
and Silurian dolomites over which the eastern margin of the lobe passed.Payson till from the Lake Michigan lobe contains markedly more dolomite
than calcite throughout most of its extent, but as the Mississippi River Valley is
approached the ratio diminishes, and at the westernmost localities in Illinois (in
Hancock County) calcite and dolomite are approximately equal. The progressive
westward increase in calcite reflects additions from the Mississippian and Penn-sylvanian limestones and western Kansan till over which the Payson glacier passed.
In all other Illinoian and Wisconsinan tills in Illinois, dolomite exceedscalcite (table 5, 6). In contrast, the eastern Kansan till in east-central and south-
ern Illinois contains more calcite than dolomite. This relation suggests that the
source of the material was from the Lake Erie lobe (Dreimanis and Reavely, 1953;
Anderson, 1957; Harrison, 1959, 1960).
SUMMARY AND CONCLUSIONS
Illinois, by virtue of its geographic position, is unique among regions in
North America that were invaded by continental glaciers because it was invaded
by glaciers from sources lying both to the northwest and to the northeast. Becausethe mineral composition of the rocks underlying these source regions are signifi-
cantly different, strong contrasts occur in the mineralogy of the several tills in
Illinois
.
Nebraskan glaciers apparently reached only into the western part of the
state and, as exposures of this till are exceedingly rare in Illinois, the mineral-
ogical data presented here are from the Nebraskan west of Mississippi River.
Kansan glaciers entered the state from the northwest, south of Carroll County and
north of Calhoun County, and extended eastward approximately to the position of
the present Illinois River. A Kansan glacier also entered Illinois from the east
and, although it extended to the vicinity of St. Louis, it approached but did not
cross the position of Illinois Valley.
During the Illinoian Stage a major lobe of ice entered the state by way of
the Lake Michigan basin. In the east-central and southern parts of Illinois, the
Lake Michigan lobe glacier was deflected to the west by lobes advancing from
farther east, from the Lake Huron and possibly Erie basins. The latter extended
to the Mississippi River Valley from St. Louis to Chester. The deflected Lake
Michigan lobe spread westward across the Ancient Mississippi Valley ( the present
MINERALOGY OF GLACIAL TILLS 11
Illinois Valley) and crossed the present Mississippi River Valley in the area from
Hancock County to Rock Island County. The northeast- southwest belt of ridged
drift in the Kaskaskia Valley is an interlobate morainic complex marking the con-
tact of the Saginaw-Erie lobe with the Lake Michigan lobe.
The Illinoian Stage is complex but two major episodes of retreat and read-
vance resulted in deposition of the Jacksonville and Buffalo Hart end moraineswhich serve as a basis for three substages— Payson, Jacksonville, and Buffalo
Hart. The Payson may include a major retreat and readvance. In large areas final
wastage of the Payson glacier was by stagnation.
During the Altonian Substage of the Wisconsinan, glacial lobes from GreenBay, from the Lake Michigan basin, and probably also from farther east entered
Illinois and extended as far south as Vermillion County. A major ice withdrawaloccurred during Farmdalian time. During the Woodfordian Substage, the most ex-
tensive of the Wisconsinan glacial advances were made by the Lake Michigan and
Saginaw-Erie lobes. These lobes withdrew by a series of pulses that gave rise
to more than 30 named moraines.
The Valders glacier advanced through both Green Bay and the Lake Michi-gan basin but did not reach as far south as Illinois.
The glacial lobes that entered Illinois transported materials from five
source-provinces that are distinctive mineralogically. The first of these is the
northwestern source, represented in Illinois by tills deposited by the Nebraskanand Kansan glaciers that entered the state from Iowa and Missouri. The secondand third source areas lie to the north and northeast and are represented by tills
that were brought into Illinois by way of the Green Bay and Lake Michigan lobes,
the fourth source area is farther east, more directly northeast, and is shown bythe tills that were derived from the Saginaw (Lake Huron) lobe, and the fifth source
area is still farther east and is represented by the tills that were derived from the
Lake Erie lobe.
Tills from the western source are characterized by considerably more epi-
dote than garnet and relatively large amounts of kyanite, staurolite, and andalu-
site among the heavy minerals. Among the clay minerals, montmorillonite is dom-inant (always more than 60%) and chlorite is virtually absent. Calcite is moreabundant than dolomite
.
Tills from the Lake Michigan lobe are characterized by approximately equal
amounts of garnet and epidote, although epidote becomes relatively more abun-
dant in the younger tills within the lobe. They contain more potash feldspars than
tills from other lobes. Illite is dominant among the clay minerals and chlorite is
consistently present. Dolomite is more abundant than calcite.
Tills from the Green Bay lobe are similar to the tills of the Lake Michiganlobe but have a much higher content of expansible minerals derived from the alter-
ation of chlorite and possibly biotite micas and have a higher content of epidote.
Tills from source areas lying east of the Lake Michigan lobe are character-
ized by much larger amounts of garnet than epidote, by the dominance of illite, andby the presence of both kaolinite and chlorite. Tills deposited by glaciers that
advanced across Michigan and northern Indiana from the position of Saginaw Baycontain more dolomite than calcite, whereas the tills from the Lake Erie lobe con-tain more calcite than dolomite.
The mineral composition of the tills derived from each of these source areas
was progressively modified by the erosion of local bedrock and of older Pleistocene
deposits along the route of advance.
28 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Such modifications are well illustrated by the progressive westward in-
crease in montmorillonite in the Payson till, the source of the montmorillonite
being the western Kansan till and the western-derived Petersburg Silt over whichthe Payson glacier advanced.
In addition to characterizing the composition of the tills derived from the
several source regions, the mineralogical data presented here also serve as a
means of differentiating stratigraphic units. Western Kansan till can be readily
distinguished from the overlying lUinoian by its much higher content of epidote than
garnet whereas in the Illinoian these two minerals appear in about equal proportion,
by their higher percentage of staurolite, by their higher content of montmorillonite,
and by their high calcite content versus the high dolomite content of the Illinoian.
Eastern Kansan is everywhere distinguishable from the overlying Illinoian by its
higher percentage of calcite than dolomite, but it also generally has a higher per-
centage of hypersthene and diopside-augite and a lower percentage of tourmaline
and zircon.
Among the Illinoian tills deposited by the Lake Michigan lobe the percentage
of montmorillonite is generally higher in the Payson than in the Jacksonville and
much higher than in the Buffalo Hart; the Jacksonville is generally lower in kao-
linite and chlorite than either the Buffalo Hart or Payson tills.
Among the Wisconsinan tills the Winnebago is distinguished from LakeMichigan lobe Illinoian by the facts that its montmorillonite content is largely
derived from expansible chlorite, vermiculite, and biotite micas and that it con-
tains no kaolinite, whereas all Illinoian tills contain some kaolinite. The Wood-fordian tills are distinguished from Payson, Jacksonville, and Winnebago tills bytheir much lower content of montmorillonite and from the Buffalo Hart till by the
general absence of kaolinite in the Woodfordian tills; also, the Woodfordian tills
generally contain more epidote than do the Illinoian.
MINERALOGY OF GLACIAL TILLS 29
REFERENCES
Anderson, R. C, 1957, Pebble and sand lithology of the major Wisconsin glacial
lobes of the central lowland: Geol. Soc. America Bull., v. 68, p. 1415-1449.
Andrews, G. W. , 1958, Windrow Formation of Upper Mississippi Valley region-A sedimentary and stratigraphic study: Jour. Geology, v. 65, p. 597-624.
Arneman, H. F., and Wright, H. E., 1959, Petrography of some Minnesota tills:
Jour. Sed. Petrology, v. 29, p. 540-554.
Ball, J, R., 1940, Elongate drift hills of southern Illinois: Geol. Soc. AmericaBull., V. 51, no. 7, p. 951-970.
Ball, J. R., 1952, Geology and mineral resources of the Carlinville Quadrangle:
Illinois Geol. Survey Bull . 77, p. 110.
Beavers, A. H., Johns, W. D., Grim, R. E., and Odell, R. T., 1955, Clayminerals in some Illinois soils developed from loess and till under grass
vegetation: National Academy of Sciences-National Research Council, Third
National Conference on Clays and Clay Minerals Proc, Pub. 395, p. 356-372.
Bell, A. H., and Leighton, M. M., 1929, Nebraskan, Kansan and Illinoian tills
near Winchester, Illinois: Geol. Soc. America Bull., v. 40, no. 2, p. 481-490.
Brophy, J. A., 1959, Heavy mineral ratios of Sangamon weathering profiles in
Illinois: Illinois Geol. Survey Circ. 273.
Brown, B. E., and Jackson, M. L., 1958, Clay mineral distribution in Hiawathasandy soils of Wisconsin: NAS-NRC, Fifth Natl. Conf. on Clays and Clay
Minerals Proc, Pub. 566, p. 213-226.
Dreimanis, A,, 1960, Pre-classical Wisconsin in the eastern portion of the Great
Lakes region. North America: Internatl . Geol. Cong., 21st Session, Norden,
pt. IV, p. 108-119.
Dreimanis, A., and Reavely, G. H., 1953, Differentiation of the lower and the
upper till along the north shore of Lake Erie: Jour. Sed. Petrology, v. 23,
p. 238-259.
Dreimanis, A., Reavely, G. H., Cook, R. J. B., Knox, K. S., and Moretti, F. J.,
1957, Heavy mineral studies in tills of Ontario and adjacent areas: Jour. Sed.
Petrology, v. 27, p. 148-161.
Droste, J. B., 1956, Clay minerals in calcareous till in northeastern Ohio: Jour.
Geology, v. 64, p. 187-190.
Ekblaw, G. E., and Willman, H. B., 1957, Farmdale drift near Danville, Illinois:
Illinois Acad. Sci. Trans., v. 47, p. 129-138.
Eveland, H. E., 1952, Pleistocene geology of the Danville region, Illinois:
Illinois Geol. Survey Rept. Inv. 159.
30 ILLINOIS STATE GEOLOGICAL SURVEY CIRCULAR 347
Flint, R. F., Colton, R. B., Goldthwait, R. P., and Willman, H. B., 1959,Glacial map of the United States east of the Rocky Mountains: New York,
Geol. Soc. America.
Frye, J. C, Glass, H. D., and Willman, H. B., 1962, Stratigraphy and miner-
alogy of the Wisconsinan loesses of Illinois: Illinois Geol. Survey Circ. 334.
Frye, J. C, and Leonard, A, B., 1952, Pleistocene geology of Kansas: KansasGeol. Survey Bull. 99.
Frye, J. C, and Leonard, A. B., 1954, Significant new exposures of Pleistocene
deposits at Kirwin, Phillips County, Kansas: Kansas Geol. Survey Bull . 109,
Pt. 3, p. 29-48.
Frye, J. C, and Willman, H. B., 1960, Classification of the Wisconsinan Stage
in the Lake Michigan glacial lobe: Illinois Geol. Survey Circ. 285.
Frye, J. C, and Willman, H. B., 1963, Development of Wisconsinan classifica-
tion in Illinois related to radiocarbon chronology: Geol . Soc . America
Bull., v. 74; in press .
Frye, J. C, Willman, H. B., and Glass, H. D., 1960, Gumbotil, accretion-gley,
and the weathering profile: Illinois Geol. Survey Circ. 295.
Gravenor, C. P., 1954, Mineralogical and size analysis of weathering zones on
Illinoian till in Indiana: Am. Jour. Sci., v. 252, p. 159-171.
Hackett, J. E., 1960, Ground-water geology of Winnebago County, Illinois:
Illinois Geol. Survey Rept. Inv. 213.
Harrison, W., 1959, Petrographic similarity of Wisconsin tills in Marion County,
Indiana: Indiana Geol. Survey Rept. Prog. 15.
Harrison, W., 1960, Original bedrock composition of Wisconsin till in central
Indiana: Jour. Sed. Petrology, v. 30, no. 3, p. 432-446.
Horberg, Leland, 1950, Bedrock topography of Illinois: Illinois Geol . Survey
Bull. 73.
Horberg, Leland, 1953, Pleistocene deposits below the Wisconsin drift in north-
eastern Illinois: Illinois Geol. Survey Rept. Inv. 165.
Horberg, Leland, 1955, Radiocarbon dates and Pleistocene chronological problems
in the Mississippi Valley Region: Jour. Geology, v. 63, p. 278-286.
Horberg, Leland, 1956, Pleistocene deposits along the Mississippi Valley in
central-western Illinois: Illinois Geol. Survey Rept. Inv. 19 2.
Johnson, W. H., 1961, Weathering profile information on some Wisconsinan end
moraines in east central Illinois: Univ. Illinois [Urbana] unpublished M.S.
thesis
.
MINERALOGY OF GLACIAL TILLS 31
Johnson, W. H., 1962, Stratigraphy and petrography of Illinoian and Kansan drift
in central Illinois: Univ. Illinois [Urbana] unpublished Doctoral Dissertation.
Kay, G. F., and Graham, J. B., 1943, The Illinoian and post-IUinoian Pleistocene
geology of Iowa: Iowa Geol. Survey, v. 38, p. 1-262.
Kempton, J. P., 1962, Stratigraphy of the glacial deposits in and adjacent to Troy
bedrock valley, northern Illinois: Univ. Illinois [Urbana] unpublishedDoctoral Dissertation.
Leighton, M. M., and Brophy, J. A., 1961, Illinoian glaciation in Illinois:
Jour. Geology, v. 69, p. 1-31.
Leighton, M. M., and Willman, H. B., 1950, Loess formations of the MississippiValley: Jour. Geology, v. 58, p. 599-623.
Leonard, A. B., and Frye, J. C., 1960, Wisconsinan moUuscan faunas of the
Illinois Valley region: Illinois Geol. Survey Circ. 304.
Leverett, Frank, 1899, The Illinois glacial lobe: U. S. Geol. Survey Mon., v. 38.
MacClintock, Paul, 1929, Recent discoveries of pre-Illinoian drift in southern
Illinois: Illinois Geol. Survey Rept. Inv. 19, p. 27-57.
Murray, H. H., and Leininger, R. K., 1956, Effect of weathering on clay minerals:
NAS-NRC, Fourth Natl. Conf. on Clays and Clay Minerals Proc, Pub. 456,
p. 340-347.
Murray, R. C, 1953, The petrology of the Gary and Valders tills of northeastern
V\^isconsin: Am. Jour. Sci., v. 251, p. 140-155.
Ruhe, R. v., 1956, Geomorphic surfaces and the nature of soils: Soil Science,
V. 82, p. 441-455.
Shaffer, P. R., 1956, Farmdale drift in northwestern Illinois: Illinois Geol . Sur-
vey Rept. Inv. 198.
V\^anless, H. R., 1957, Geology and mineral resources of the Beardstown, Glas-ford, Havana, and Vermont Quadrangles: Illinois Geol. Survey Bull. 82.
Wascher, H. L., Alexander, J. D., Ray, B. W., Beavers, A. H., and Odell, R. T.,
1960, Characteristics of soils associated with glacial tills in northeastern
Illinois: Univ. Illinois Agr. Exp. Sta., Bull. 665.
White, J. L., Bailey, G. W., and Anderson, J. U., 1960, The influence of parent
material and topography on soil genesis in the Midwest: Purdue Univ. Agr.
Exp. Sta. Research Bull. 693.
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TABLE 5 - AVERAGES OF CLAY MINERAL DATA BY STRATIGRAPHIC UNIT
Average Composition Range of Composition(in percent) (in percent)
S(U
a.g
c c "c fiM O rt ^ tfl
•H 4J (U <U
O OJ C -H -rH c O (U C -He j-i -^ u
JJ -H ,-1 O U -r^ r-4 Oo
Stratigraphic Unit ^ ^ tfl x; ^ ^ 1 M ^^
Wisconsinan
Woodfordian
Winnebago
Illinoian
Buffalo Hart
•Tacksonville
Southeast
Payson
Petersburg Silt
Kansan
Western Kansan west of
4th principal meridian
Western Kansan east of
4th principal meridian
Eastern
40 69
12 21 68
17 16 63
47 36 45
20 66 19
13 43 35 22
0-19 62-92 7-30
15_42 40-72 10-27
0-14 55-90 8-41
11-28 60-82 4-14
12-28 47-76 9-39
17-64 19-69 7-34
47-85 6-43 8-25
35-50 25-44 14-29
0-24 47-79 17-40
Nebraskan
TABLE 5 - Continued
The above averages are based on the following samples
:
Woodfordian: P-130, 138, 139, 145, 146, 148, 170, 344, 346, 347, 349, 350, 355,
356, 371, 372, 384, 388, 390, 391, 392, 394, 399, 400, 401, 402, 403, 404,
405, 407, 495, 496, 549, 558, 566, 696, 697, 724, 726, 727, 744, 745, 747,
819, 826, 1249, 1270, 1393, 1487
HK-21, 13054-10, 13054-20, 13054-25, 13054-45, 13054-50, 13054-55, 13054-60,
13054-65, 13054-70, 13054-75, 13054-80
Winnebago: P-411, 412, 415, 418, 421, 431, 698, 705, 706, 713
Buffalo Hart: P-126, 131, 180, 181, 182, 312, 327, 357, 369, 374, 376, 542, 550,
559, 674A, 687, 732, 777A, 777B, 778, 945, 946, 971, 972, 1181, 1461, 1470,
1472, HK-3, HK-4, 11269-25, 11269-30, 11269-35, 21158-20, 21158-25, 22409-15,22409-20, 22409-25, 22409-55, 22409-70
Jacksonville: P-94, 97, 335, 365, 619, 750, 762, 763, 970, 1394, 1434, 1435
Illinoian (Southeast): P-172, 195, 196, 197, 450, 977, 978, 1063, 1133, 1157,
1165, 1169, 1172, 1174, 1175, 1284, 1321
Payson: P-1, lA, 26, 46, 95, 113, 125, 277, 541, 581, 582, 616, 631, 947, 949,
951, 954, 1237, 1383, 1498, 1516, HK-2, HK-44, HK-45, HK-46, HK-49, HK-50,HK-51, HK-52, HK-53, HK-54, HK-55, HK-56, HK-106, HK-117, HK-118, HK-119,HK-120, HK-144, HK-145, HK-153, HK-154, 11269-40, 13054-165, 13054-170,21158-35, 21158-40
Petersburg Silt: P-90, 91, 613, 613A, 614, 615, HK-32, HK-33, HK-34, HK-35,
HK-36, HK-37, HK-38, HK-39, HKW-107, HKW-108, HKW-109, HKW-121, HKW-122,21158-45
Kansan (Western)
West of 4th principal meridian: P-61, 63, 65, 301, 508, 509, 538, 603A, 612A,
796, 952, 953, 1201, 1203, 1204, 1205, 1206, 1207, 1252, 1294, 1302, 1303,HK-23, HK-24, HK-25, HK-26, HK-27, HK-28, 21158-55, 21158-60, 21158-65,21158-70, 21158-75, 21158-80, 21158-85, 21158-90, 21158-95, 21158-100,21158-105
East of 4th principal meridian: P-119, 119A, 120, 123, 123A, 11269-60, 11269-65,11269-75, 11269-80, 13054-195, 13054-200, 13054-205, 13054-210
Kansan (Eastern): P-447, 731, 964, 964A, 964B, HK-71, HK-72, HK-73, HK-74,HKW-111, HKW-112
Nebraskan: P-502, 795, 1250, 1251
+ oO <-i
o
SELECTED GEOLOGIC SECTIONS
Following are eight of the measured geologic sections used in this report; thirty additional
sections also used in this study were published in Illinois State Geological Survey Circulars 285, 304,
and 334. The numbers enclosed in parentheses, for example (P-565), are sample numbers used in the
tables and illustrations in this report. The sections are arranged alphabetically by name.
CHAMNESS SECTION Thickness(feet)
Measured in cuts along Interstate Highway 57,
SE^ sec. 34, T. 9 S., R. 2 E., Williamson Coun-ty, Illinois (1961). This is the southern-most exposure of glacial till studied.
Thickness(feet)
Pleistoce i Seriesin Stage
4. Loess, brown to tan, darker in
lower part, leached, compact;surface soil in upper part (Sample
P-1066 near base) 20.
(
Illinoian Stage
3. Sangamon Soil B-zone; clay withsome silt, brown to red-brown,leached, compact, sharp contactat top (Sample P-1065) 2.(
2. Till, silty and clayey, pinkishtan in lower part grading upwardto red-brown, jointed, calcareous,massive; very few scattered peb-bles; gradational top and bottomSample P-1064) 2.i
1. Till, tan, silty, compact, massive,calcareous; scattered pebbles upto 2 inches in maximum diameter;well developed joints with calcitefilling approximately 1/3" thickalong joint planes; base on Penn-sylvanian sandstone (P-1063,lower) 5.C
Total 29.!
FLAT ROCK SECTION
Measured in cuts along Illinois highway 1, SWkNE^ SW% sec. 6, T. 5 N., R. 11 W. , CrawfordCounty, Illinois (1961).
Pleistocene SeriesWisconsinan Stage
4. Loess, tan-brown, leached, massive,compact; some mottling in lowerpart; surface soil in top (P-1,
(P-1160) 4.C
3. Colluvium of silt with sand, be-coming sandy and containing peb-bles in lower part; gradationalwith loess at top; tan-brown,leached (P-1159) l.C
Illinoian Stage
2. Sangamon Soil B-zone; red,
micro-blocky, compact; clay
skins, Mn-Fe pellets; grada-tional at base (P-1158) 3.(
1. Till, yellow-tan, mottled with
gray and brown, massive with some
jointing, clayey, leached, tough
(P-1157 lower) 4.(
Total 12.
(
PETERSBURG SECTION
Measured in cuts along county road in NW^ WkUEk sec. 23, T. 18 N., R. 7 W., Menard County,Illinois (1957).
Pleistocene SeriesWisconsinan StageWoodfordian SubstagePeoria Loess4. Loess, tan, massl
iurfa( lil i
;alcareous
;
Illinoian Stage3. Till, massive, calcareous, compact,
blue-gray, pebbly and cobbly (P-94,2 feet above base) ; truncated Sang-amon Soil at top ;
2. Till, silty, massive, tan; con-tains fossil snails similar to
those in the unit below (P-93 top;
P-92 bottom)Petersburg Silt1. Silt, massive, compact, gray-tan
in upper part and purplish brownin lower part, calcareous (P-91middle; P-90 lower); contains fos-sil snails in upper half; a hur-ried soil was penetrated in augerhole a few feet below base of sec-tion ;
RUSHVILLE (0.1 WEST) SECTION
Measured in new highway cuts in SW% NE% SW%sec. 23, T. 1 N., R. 1 W., Schuyler County,Illinois (1959)
Peoria Loess10. Loess, massive, gray-tan, calcar-
eous below the surface soil
(P-658, P-659, P-660 from calcar-eous loess; P-661, P-662 from sur-
face soil) 13.0
Altonian SubstageRoxana Silt
9. Loess, massive, calcareous, palepinkish to gray-tan (P-656 base;
P-657 top) 8.0
8. Loess, massive, friable, calcar-eous, medium dark gray-brown(P-655) 8.0
7, Loess, massive, pink-brown, cal-careous (P-654). 3.0
6, Loess, massive, medium gray-brown, calcareous (P-653) 5.0
5. Silt with a few pebbles and somesand (colluvium) , calcareous,gray-brown (P-652) 1.0
Illinoian Stage4. Sangamon Soil; developed in till
intermixed with silt, sand, andgravel suggesting an ice-contactdeposit (P-651 from soil; P-650from calcareous lower part) 10.0
3. Gravel, fine to coarse, poorlystratified, calcareous (P-649) 23.0
2. Till, blue-gray, massive, com-pact, calcareous, locally oxi-dized (P-648) 2.0
Pennsylvanian System1. Shale, gray 4.0
Total 77.0
RUSHVILLE (2.4 WEST) SECTION
Measured in new highway cuts in SWi; SW% NE%sec. 16, T. IN., R. 1 W., Schuyler County,Illinois (1959).
Pleistocene SeriesIllinoian Stage
4. Till, pebbly with silty matrix,calcareous in lower part (P-616)
;
well developed Sangamon Soil in
top; thickens laterally and be-comes extremely silty 8 to 20.0
Petersburg Silt3, Silt, yellow, gray and tan, calcar-
eous, banded with limonite inupper part (P-615) ;
gradational atbase; in upper part contains fossilsnails 15.0
2. Silt, pink in top (P-614) to purple-brown in lower part (P-613; P-613A)
;
some thin limonite cemented zones;basal 2 feet gray and sandy 10.0
Kansan Stage1. Till, leached, clayey, gray and
tan (P-612; P-612A) ; rests onPennsylvanian shale and clay
RUSHVILLE (4.5 WEST) SECTION
in new highway cuts in NW% SW4; SW^
:. IN., R. 1 W., Schuyler County,
(1959, 1960).
"fisconsinan StageWoodfordian SubstagePeoria Loess9. Loess, massive. tan, noncalci
well developed ssurface soil :
per partFarmdalian SubstageFarmdale Silt8. Silt, red-brown.,
massive, noi
Altonian SubstageRoxana Silt
7. Loess, massive. tan to gray.
6. Silt with some sand and a few peb-bles (colluvium), noncalcareous,gray-tan :
Illinoian Stage5. Sangamon Soil developed in till;
brown, clay-rich B-zone withMn-Fe staining on joint surfacesand in small pellets; at base gray,gradational (P-605 from B-zone) i
4. Till, gray and tan, massive, cal-careous, bouldery (P-604) i
3. Till, brown and gray, few bouldersand large cobbles, calcareous;
this zone pinches out westward;eastward sand and gravel in baseon till below. In local channelsin till below, this till inter-bedded with noncalcareous, red-brown, sandy and clayey silt(P-603F) 1-1(
Kansan Stage2. Yarmouth Soil developed in till;
dark red-brown, clay-rich B-zone(P-603 B, C, D, E), grading down-ward into tan-brown CL-zone (P-603A) (
1. Till, massive, calcareous, fine tex-tured; contains abundant shale withsome coal and weathered pebblesand cobbles; locally contains somemasses of noncalcareous sand
(P-601, P-602) 1(
Total 5'
SCHULINE SECTION
Measured in road cut and nearby creek bank, NW%NE% NE% sec. 24, T. 5 S., R. 7 W., RandolphCounty, Illinois (1961)
Thickness(feet)
Pleistocene SeriesWisconsinan StageWoodfordian SubstagePeoria Loess9. Loess, massive, friable, light
brown to tan with gray-tan mot-tles, leached; surface soil in
top (P-1053 at base to P-1057from B-zone of surface soil) 6.5
Altonian SubstageRoxana Silt
8. Loess, massive, reddish brown, mot-tled with and containing blackstreaks and pellets of Mn-Fe; weath-ers to a platy structure (P-1050base; P-1051; P-1052 top) 2.5
Sangamonian Stage7. Sangamon Soil; colluvium of silt,
sand and some clay, brown, tan andgray micro-mottled, leached; con-tains a few small pebbles; atten-uated A-zone and upper part of theB-zone of the Sangamon Soil; upperpart gradational upward with over-lying Roxana Loess (P-1048 base;P-1049 top) 2.0
Illinoian Stage6. Sangamon Soil B-zone; developed in
till, brown, becoming darker up-ward, mottled with light tan at
top, oxidized and leached; Mn-Fepellets and crust on joint surfaces;laterally grades into a BG-zoneand at base is gradational with CL-zone (P-1042 BG-zone; P-1043top of CL-zone; P-1044 to P-1047upward through B-zone) 3.5
5. Till (CL-zone), oxidized, leached,tan-brown with some staining withMn-Fe (P-1040 base; P-1041 top) 2.0
4. Till, calcareous, mottled grayand tan-brown; some CaC03 nodulesnear top; well jointed with jointplanes marked by gray zones bor-dered by limonite rinds (P-1037
base; P-1038; P-1039 top) 5.5Petersburg Silt3. Silt, massive, pinkish brown with
gray mottles, generally noncalcar-eous but locally weakly calcareousand sparsely fossiliferous in up-per part; locally in upper parttill interbedded with gray silt(P-1033, 3 feet above base, to
P-1036 top) 7.0
2. Silt, gray with a few rusty streaks,contains some clay, massive, Mn-Fepellets and nodules in lower part(P-1032 base) :
1 . Covered to level of abandonedcreek channel (
Total 3'
TINDAIL SCHOOL SECTION
Measured in borrow pit excavation along northbluff of Illinois River Valley, SW^ NE^ sec. 31,T. 7 N., R. 6 E., Peoria County, Illinois(1957, 1958, and 1960).
Pleistocene SeriesWisconsinan StageWoodfordian SubstagePeoria Loess16. Loess, massive, upper 5 feet
leached and contains soil pro-file; lower part weakly calcar-eous, tan to gray; streaked withlimonite tubules, scatterednodules and indistinct lamin-ation 12.0
Farmdalian and Altonian SubstagesFarmdale and Roxana Silts
15. Silt, massive to laminated,weakly calcareous in mid-part butnoncalcareous above and below,light gray with thin, dark, humicbands in upper part, 4.5
Illinoian Stage14. Sangamon Soil, A and G-zones,
leached; top 1 foot of A-zonedark gray, granular to massive,grading downward into massivegley, gray mottled with tan 5.0
13. Till (Buffalo Hart), gray, thoroughlyinterlaced with veinlets of hardlimonite, brown, noncalcareous in
gray matrix but locally calcar-eous in iron-cemented veinlets 2,0
12, Till, calcareous, unevenly oxi-dized, well jointed, gray-tan,gradational at top and bottom(P-126) 3.0
11. Silt and some sand, red, tan, andgray; thin zones cemented withCaC03; southward the silts pinchout and a cobble zone is at samestratigraphic position 2.0
10, Till, oxidized, calcareous,jointed, brown 3,0
9. Sand and gravel in discontinuouslenses, locally cemented, brown 3.0
8. Till (Payson), calcareous, pebbly,blue-gray, well jointed throughout
with oxidized rinds on joints(P-125 three feet above base) 18,0
(fee
Kansan Stage7. Yarmouth Soil, truncated to the
B„-horizon at top, leached, clayey,
dark brown; locally spots of sec-ondary carbonate; siliceous peb-bles and cobbles present through-out; gradational with calcareoustill at base and sharp contact at
top except locally where blocks of
this soil are incorporated in
overlying till (P-124)
6. Till, calcareous, gray with mot-tled patches of brown (P-123A) in
upper part, jointed throughout withoxidized rinds along joints; len-ticular, irregular masses of graysilt and fine sand incorporated in
middle part (P-123)
5. Sand, fine to medium, calcareous,brown with locally dark graystreaks at top; upper and lowercontacts irregular (P-122)
4. Silt and very fine sand, massive to
laminated, gray; locally softlimonite in streaks and contortedbands (P-121; P-121A)
3. Till, compact, clayey, calcareous,oxidized; contains scattered peb-bles and cobbles, streaks and podsof silt, and flakes of coal(P-120)
2, Till, compact, calcareous, clayey,blue-gray (P-119; P-119A)
1. Silt, calcareous, gray, containsfossil snails
Total '.
Illinois State Geological Survey Circular 347
55 p. , 9 figs. , 6 tables
8 geol. sections, 1963
Printed by Authority of State of Illinois, Ch. 127. IRS, Par. 58.25.
CIRCULAR 347
ILLINOIS STATE GEOLOGICAL SURVEYURBANA